Abstract: Flexible uniform pressure loading is the premise to enhance the accuracy of geomechanical model test. A new flexible uniform pressure loading system is developed, which includes hydraulic automatic control system and flexible uniform pressure loading device. Hydraulic automatic control system can be operated easily and controls the 12-exact servo pressure loading with longtime stability or unloading automatically. Flexible uniform pressure loading device is composed of the hydraulic cylinder, rigid thruster and flexible transfer rubber pad etc.; the reasonable thickness of flexible transfer rubber pad is 50 mm determined by numerical method. The system is applied to the model test with uneven surface and compared with the rigid loading. The results show that the effect of flexible uniform pressure loading device is more significant to rigid loading. The model initial stress field depends on the Shore hardness of uniformity transmission rubber pads, loading stress and depth from the surface. The Shore hardness of rubber is lower, the model initial stress field is more even; and model initial stress field becomes uniform with the loading increasing and depth increasing. The model stress of depth 130 mm from surface is uniform using flexible uniform pressure loading. Test result shows that the flexible uniform pressure loading system improves the accuracy of pressure loading and can be applied to model test widely.

Key words: geomechanical model test, uniform pressure loading, system development, flexible rubber, test application